There is an input device using a sensor, such as a touch panel, as a controller for a GUI (Graphical User Interface) widely used as a smart phone, a tablet terminal or the like.
In an input device of the related art, a sensor is mainly provided in only a surface on which a display unit is provided. However, in such an input device, a manipulation input is performed from the surface, such that information displayed on the display unit is hidden by a finger, which deteriorates operability. In recent years, as resolution in a display unit has become higher, operability is considered to be further deteriorated. Further, an input manipulation from the surface is easily seen by others and, for example, when highly confidential information such as a password number is input, it is difficult to hide the input information. Further, with the recent increase in touch manipulation variations, operations (gestures) upon input manipulation conflict such that malfunction easily occurs and the operability is deteriorated.
In recent years, touch panels capable of simultaneously detecting contacts of a plurality of fingers, that is, so-called multi-touch, have also begun to spread. Further, as a plurality of sensors is included in a device, improvement of operability has been realized (e.g., Patent Literatures 1 and 2). In such a device, as one touch sensor is provided in an opposite surface (a back surface) of a display unit of the device to detect contact of a finger, a manipulation input can be performed on a side of the back surface, and a display screen is not hidden by a finger even when the device is small. Further, intuitive interaction or expansion of a manipulation system, which has not been realized in a touch panel with a plurality of sensors in related art, can be realized.